gst/gststructure.c: No need to memset, we can clear the value ourselves.

gst/gststructure.c: No need to memset, we can clear the value ourselves.

Original commit message from CVS:
* gst/gststructure.c: (gst_structure_id_empty_new_with_size):
No need to memset, we can clear the value ourselves.
* gst/gstvalue.c: (gst_type_is_fixed),
(gst_value_get_compare_func):
Some optimisations from a few callgrind sessions:
When checking if a type is fixed, check for trivial fundamental types
first before checking types for which we need to get the type followed
by the heavy duty type checks, this reduces the amount of
g_type_fundamental() calls a lot.
When getting the compare function, first check for our registered types.
If that fails, do the heavy duty g_type_is_a() checks, reduces the
amount of g_type_is_a() considerably.